Iodide-induced chemokines and genes related to immunological function in cultured human thyroid follicles in the presence of thyrotropin

DNA Methylation in Autoimmune Thyroid Disease

Graves disease and Hashimoto disease form part of the spectrum of autoimmune thyroid disease (AITD), to which genetic and environmental factors are recognized contributors. Epigenetics provides a potential link between environmental influences, gene expression, and thyroid autoimmunity. DNA methylation (DNAm) is the best studied epigenetic process, and global hypomethylation of leukocyte DNA is reported in several autoimmune disorders. This review summarizes the current understanding of DNAm in AITD. Targeted DNAm studies of blood samples from AITD patients have reported differential DNAm in the promoter regions of several genes implicated in AITD, including TNF, IFNG, IL2RA, IL6, ICAM1, and PTPN22. In many cases, however, the findings await replication and are unsupported by functional studies to support causal roles in AITD pathogenesis. Furthermore, thyroid hormones affect DNAm, and in many studies confounding by reverse causation has not been considered. Recent studies have shown that DNAm patterns in candidate genes including ITGA6, PRKAA2, and DAPK1 differ between AITD patients from regions with different iodine status, providing a potential mechanism for associations between iodine and AITD. Research focus in the field is moving from candidate gene studies to an epigenome-wide approach. Genome-wide methylation studies of AITD patients have demonstrated multiple differentially methylated positions, including some in immunoregulatory genes such as NOTCH1, HLA-DRB1, TNF, and ICAM1. Large, epigenome-wide studies are required to elucidate the pathophysiological role of DNAm in AITD, with the potential to provide novel diagnostic and prognostic biomarkers as well as therapeutic targets.

Role of Jumonji domain-containing protein D3 and its inhibitor GSK-J4 in Hashimoto's thyroiditis

Hashimoto's thyroiditis (HT) is an autoimmune illness caused by a combination of genetic, epigenetic, and environmental factors. The pathogenesis of HT is not fully elucidated, especially in epigenetics. The epigenetic regulator Jumonji domain-containing protein D3 (JMJD3) has been extensively investigated in immunological disorders. This study has been performed to explore the roles and potential mechanisms of JMJD3 in HT. Thyroid samples from patients and healthy subjects were collected. We first analyzed the expression of JMJD3 and chemokines in the thyroid gland using real-time PCR and immunohistochemistry. In vitro, the apoptosis effect of the JMJD3-specific inhibitor GSK-J4 on the thyroid epithelial cell line Nthy-ori 3-1 was evaluated using FITC Annexin V Detection kit. Reverse transcription-polymerase chain reaction and Western blotting were applied to examine the inhibitory effect of GSK-J4 on the inflammation of thyrocytes. In the thyroid tissue of HT patients, JMJD3 messenger RNA and protein levels were substantially greater than in controls (P < 0.05). Chemokines C-X-C motif chemokine ligand 10 (CXCL10) and C-C motif chemokine ligand 2 (CCL2) were elevated in HT patients, and thyroid cells with stimulation of tumor necrosis factor α (TNF-α). GSK-J4 could suppress TNF-α-induced synthesis of chemokines CXCL10 and CCL2 and prohibit thyrocyte apoptosis. Our results shed light on the potential role of JMJD3 in HT and indicate that JMJD3 may become a novel therapeutic target in HT treatment and prevention.

Iodide-sensitive Graves' hyperthyroidism and the strategy for resistant or escaped patients during potassium iodide treatment

The effectiveness of potassium iodide (KI) (100 mg/day) was evaluated in 504 untreated patients with Graves' hyperthyroidism (GD). Initial response to KI within 180 days, the effect of additional methylmercaptoimidazole (MMI) or radioactive iodine (RI) in resistant or escaped patients, and long-term prognosis were evaluated. Serum fT₄ levels became low or normal in 422 patients (83.7%, KI-sensitive group) without serious side effects. Among these patients, serum TSH levels became high (n = 92, hypothyroid) or normal (n = 78) in 170 patients (33.7%) (KI-sensitive with a recovered TSH response, Group A), but remained suppressed in 252 patients (50.0%) (KI-sensitive with TSH suppression, Group B). Serum fT₄ levels decreased but remained high in 82 patients (16.3%) (KI-resistant, Group C). Older patients, or those with small goiter and mild GD were more KI-sensitive with a recovered TSH response than others. Escape from KI effect occurred in 0%, 36% and 82% in Group A, B and C, respectively. Patients in Group B and C were successfully treated with additional low-dosage MMI or RI. After 2-23 years' treatment (n = 429), remission (including possible remission) and spontaneous hypothyroidism were significantly more frequent in Group A (74.3% and 11.1%, respectively,) than in Groups B (46.3% and 2.8%, respectively) or C (53.6% and 1.5%, respectively) (p < 0.0001). In conclusion, a high KI sensitivity with a recovered TSH response was observed in about a third of the patients in GD associated with a better prognosis. Additional MMI or RI therapy was effective in escaped or KI-resistant patients with suppressed TSH level.

Changes in histone H3 lysine 4 trimethylation in Hashimoto's thyroiditis

INTRODUCTION

The precise pathogenesis of Hashimoto's thyroiditis (HT) is yet to be fully elucidated. The role of epigenetics in the pathogenesis of HT has scarcely been addressed. Tri-methylated histone H3 lysine 4 (H3K4me3) is generally regarded as a marker of gene activation. The aim of this study was to explore genome-wide H3K4me3 patterns and global protein levels in primary thyrocytes and thyroids from HT patients.

MATERIAL AND METHODS

Chromatin immunoprecipitation sequencing (ChIP-seq) was used to analyze genome-wide H3K4me3 patterns in primary cultured thyrocytes from three HT females and three age-matched female control subjects. Western blotting was used to analyze global H3K4me3 levels in thyrocytes and thyroid tissues. Gene expression was determined using RT-PCR. Mixed-lineage leukemia 1 (MLL1) protein levels were measured by western blotting and immunohistochemistry.

RESULTS

Nine genes - TG, CXCL8, CCL2, CXCL10, FASLG, ICAM1, ITGA4, IL18 and TRAIL - showed increased H3K4me3 enrichment in promoter regions around the transcriptional start sites, and gene expression of ICAM1, CCL2 and CXCL8 was consistently increased (p < 0.05). KEGG pathway analysis suggested that differential peak-related genes were markedly associated with autoimmune thyroid disease< 0.05).

CONCLUSIONS

This first investigation of genome-wide H3K4me3 distribution in thyroid follicular cells suggested that genes associated with autoimmune thyroiditis showed differential H3K4me3 enrichment, which was partly related to gene expression. Global H3K4me3 changes and increased MLL1 expression were found in thyroid tissues from HT patients.

Kopp P, Habeos I, Trougakos IP, Khoo NKH, Sykiotis GP. The Transcriptomic Response of the Murine Thyroid Gland to Iodide Overload and the Role of the Nrf2 Antioxidant System

Background: Thyroid follicular cells have physiologically high levels of reactive oxygen species because oxidation of iodide is essential for the iodination of thyroglobulin (Tg) during thyroid hormone synthesis. Thyroid follicles (the functional units of the thyroid) also utilize incompletely understood autoregulatory mechanisms to defend against exposure to excess iodide. To date, no transcriptomic studies have investigated these phenomena in vivo. Nuclear erythroid factor 2 like 2 (Nrf2 or Nfe2l2) is a transcription factor that regulates the expression of numerous antioxidant and other cytoprotective genes. We showed previously that the Nrf2 pathway regulates the antioxidant defense of follicular cells, as well as Tg transcription and Tg iodination. We, thus, hypothesized that Nrf2 might be involved in the transcriptional response to iodide overload. Methods: C57BL6/J wild-type (WT) or Nrf2 knockout (KO) male mice were administered regular water or water supplemented with 0.05% sodium iodide for seven days. RNA from their thyroids was prepared for next-generation RNA sequencing (RNA-Seq). Gene expression changes were assessed and pathway analyses were performed on the sets of differentially expressed genes. Results: Analysis of differentially expressed messenger RNAs (mRNAs) indicated that iodide overload upregulates inflammatory-, immune-, fibrosis- and oxidative stress-related pathways, including the Nrf2 pathway. Nrf2 KO mice showed a more pronounced inflammatory–autoimmune transcriptional response to iodide than WT mice. Compared to previously published datasets, the response patterns observed in WT mice had strong similarities with the patterns typical of Graves’ disease and papillary thyroid carcinoma (PTC). Long non-coding RNAs (lncRNAs) and microRNAs (miRNAs) also responded to iodide overload, with the latter targeting mRNAs that participate mainly in inflammation pathways. Conclusions: Iodide overload induces the Nrf2 cytoprotective response and upregulates inflammatory, immune, and fibrosis pathways similar to autoimmune hyperthyroidism (Graves’ disease) and PTC.

Intrathyroid injection of dexamethasone inhibits Th2 cells in Graves' disease

OBJECTIVE

Intrathyroid injection of dexamethasone (IID) was used for decrease the relapse rate of hyperthyroidism in the treatment of Graves' disease (GD), but the mechanism is still unclear. We aimed to explore the effect of IID on T help (Th)1/Th2 cells and their chemokine in patients with GD.

SUBJECTS AND METHODS

A total of 42 patients with GD who were euthyroidism by methimazole were randomly divided into IID group (n = 20) and control group (n = 22). Thyroid function and associated antibody, Th1/Th2 cells proportion, serum CXCL10 and CCL2 levels, and CXCR3/CCR2 mRNA expression in peripheral blood mononuclear cells before and after 3-month IID treatment were tested by chemiluminescence assay, Flow cytometry, ELISA, and real-time PCR, respectively. Thyroid follicular cells were stimulated by IFN-γ and TNF-α and treated with dexamethasone in vitro. CXCL10 and CCL2 levels in supernatant were determined.

RESULTS

After 3-month therapy, the proportion of Th2 cells and serum CCL2 levels, as well as TPOAb, TRAb levels and thyroid volume decreased in IID group (p < 0.05). However, the proportion of Th1 and CXCL10 levels had no change in IID group and control (p > 0.05). The CXCR3/CCR2 ratio had no change in both groups (p > 0.05).

CONCLUSION

IID therapy could inhibit peripheral Th2 cells via decreasing CCL2 level in peripheral blood, and this result partly explain the effects of IID therapy on prevention of relapse of GD. Arch Endocrinol Metab. 2020;64(3):243-50.

Roles of Endogenous IL-10 and IL-10-Competent and CD5+ B Cells in Autoimmune Thyroiditis in NOD.H-2h4 Mice

Interleukin (IL)-10 is a highly important anti-inflammatory cytokine in the immune system. CD1dhi and CD5+ B cells are both traditionally defined IL-10-secreting B cells. In recent years, a B cell group with combined markers of CD1dhi and CD5+ has been widely studied as it has been reported to suppress autoimmunity in mouse models of autoimmune diseases through IL-10 mechanisms. From the perspective of origination, CD1dhi and CD5+ B cells are developed from different B cell lineages. Whether the regulatory capacity of these 2 B cell groups is consistent with their ability to secrete IL-10 has not been determined. In this study, we generated IL-10 knockout NOD.H-2h4 mice to investigate the function of endogenous IL-10 in autoimmune thyroiditis and conducted adoptive transfer experiments to explore the respective roles of CD5+ and CD1dhi B cells. In our results, the IL-10-/- NOD.H-2h4 mice developed thyroiditis, similar to wild-type NOD.H-2h4 mice. The CD5+ B cells were more capable of secreting IL-10 than CD1dhi B cells in flow cytometric analysis, but the CD1dhi B cells showed more suppressive effects on thyroiditis development and autoantibody production, as well as Th17 cell response. In conclusion, endogenous IL-10 does not play an important role in autoimmune thyroiditis. CD1dhi B cells may play regulatory roles through mechanisms other than secreting IL-10.

Metabolomics evaluation of repeated administration of potassium iodide on adult male rats

The long-lasting consequence of a new iodine thyroid blocking strategy (ITB) to be used in case of nuclear accident is evaluated in male Wistar rats using a metabolomics approach applied 30 days after ITB completion. The design used 1 mg/kg/day of KI over 8 days. Thyroid hormones remained unchanged, but there was a metabolic shift measured mainly in thyroid then in plasma and urine. In the thyroid, tyrosine metabolism associated to catecholamine metabolism was more clearly impacted than thyroid hormones pathway. It was accompanied by a peripheral metabolic shift including metabolic regulators, branched-chain amino acids, oxidant stress and inflammation-associated response. Our results suggested that iodide intake can impact gut microbiota metabolism, which was related to host metabolic regulations including in the thyroid. As there were no clear clinical signs of dysfunction or toxicity, we concluded that the measured metabolomics response to the new ITB strategy, especially in thyroid, is unlikely to reveal a pathological condition but a shift towards a new adaptive homeostatic state, called 'allostatic regulation'. The question now is whether or not the shift is permanent and if so at what cost for long-term health. We anticipate our data as a start point for further regulatory toxicity studies.

Differential modulation of CXCL8 versus CXCL10, by cytokines, PPAR-gamma, or PPAR-alpha agonists, in primary cells from Graves' disease and ophthalmopathy

BACKGROUND

Thyrocytes secrete CXC chemokines, particularly (C-X-C motif) ligand (CXCL)8 and CXCL10; its physiopathological significance remains unclear. This study investigates the modulation of the secretion of CXCL8 vs. CXCL10, in human primary cells cultures of thyroid follicular cells (TFC) in Graves' disease (GD), and fibroblasts (OF) or preadipocytes (OP) from Graves' ophthalmopathy (GO).

METHODS

Cells were initially incubated with different concentrations of tumor necrosis factor (TNF)α (1, 5, 10 ng/mL). Then, CXCL8 and CXCL10 were measured in the supernatants of TFC, OF or OP cells basally and after 24 h of treatment with interferon (IFN)γ (1000 IU/mL) and/or TNFα (10 ng/mL), in presence/absence of the peroxisome proliferator activated receptor (PPAR)γ agonist pioglitazone (0, 0.1, 1, 5, 10, 20 μM), or the PPARα agonist fenofibrate (5, 10, 50, 100 μM).

RESULTS

CXCL8, not CXCL10, was detected in basal conditions in TFC, OF and OP. CXCL8 secretion increased dose-dependently with increasing concentrations of TNFα. CXCL10 secretion was significantly stimulated by IFNγ (P < 0.01) and not by TNFα, whereas CXCL8 was induced by TNFα (P < 0.01), and inhibited by IFNγ (P < 0.01) in TFC, OF and OP. Combining TNFα and IFNγ, the IFNγ-induced CXCL10 secretion was synergistically increased (P < 0.01) while the TNFα-induced CXCL8 secretion (P < 0.01) was reversed in all cell types. Pioglitazone had no significant effect on the secretion of CXCL8 stimulated by TNFα, while inhibited CXCL10. Fenofibrate, in presence of IFNγ plus TNFα, dose-dependently inhibited both CXCL10 and CXCL8 release.

CONCLUSION

We first show that TFC, OF, and OP secrete CXCL8 and CXCL10 differentially, sustained by specific proinflammatory cytokines or their combination. This could reflect a different role of the two chemokines in the course of the disease, as CXCL10 could be associated with the initial phase of the disease when IFNγ is preponderant, while CXCL8 could be associated with a later chronic phase of the disease, when TNFα prevails.

Effects of Preoperative Iodine Administration on Thyroidectomy for Hyperthyroidism: A Systematic Review and Meta-analysis

OBJECTIVE

The current guidelines recommend that potassium iodide be given in the immediate preoperative period for patients with Graves' disease who are undergoing thyroidectomy. Nonetheless, the evidence behind this recommendation is tenuous. The purpose of this study is to clarify the benefits of preoperative iodine administration from published comparative studies.

DATA SOURCES

We searched PubMed, Embase, Cochrane, and CINAHL from 1980 to June 2018.

REVIEW METHODS

Studies were included that compared preoperative iodine administration and no premedication before thyroidectomy. For the meta-analysis, studies were pooled with the random-effects model.

RESULTS

A total of 510 patients were divided into the iodine (n = 223) and control (n = 287) groups from 9 selected studies. Preoperative iodine administration was significantly associated with decreased thyroid vascularity and intraoperative blood loss. Significant heterogeneity was present among studies. We found no significant difference in thyroid volume or operative time. Furthermore, the meta-analysis showed no difference in the risk of postoperative complications, including vocal cord palsy, hypoparathyroidism/hypocalcemia, and hemorrhage or hematoma after thyroidectomy.

CONCLUSION

Preoperative iodine administration decreases thyroid vascularity and intraoperative blood loss. Nonetheless, it does not translate to more clinically meaningful differences in terms of operative time and postoperative complications.

Role of Chemokines in Thyroid Cancer Microenvironment: Is CXCL8 the Main Player?

Tumor-related inflammation does influence the biological behavior of neoplastic cells and ultimately the patient's outcome. With specific regard to thyroid cancer, the issue of tumor-associated inflammation has been extensively studied and recently reviewed. However, the role of chemokines, which play a crucial role in determining the immuno-phenotype of tumor-related inflammation, was not addressed in previous reviews on the topic. Experimental evidence shows that thyroid cancer cells actively secrete a wide spectrum of chemokines and, at least for some of them, solid scientific data support a role for these immune-active molecules in the aggressive behavior of the tumor. Our proposal for a review article on chemokines and thyroid cancer stems from the notion that chemokines, besides having the ability to attract and maintain immune cells at the tumor site, also produce several pro-tumorigenic actions, which include proangiogenetic, cytoproliferative, and pro-metastatic effects. Studies taking into account the role of CCL15, C-X-C motif ligand 12, CXCL16, CXCL1, CCL20, and CCL2 in the context of thyroid cancer will be reviewed with particular emphasis on CXCL8. The reason for focusing on CXCL8 is that this chemokine is the most studied one in human malignancies, displaying multifaceted pro-tumorigenic effects. These include enhancement of tumor cells growth, metastatization, and angiogenesis overall contributing to the progression of several cancers including thyroid cancer. We aim at reviewing current knowledge on the (i) ability of both normal and tumor thyroid cells to secrete CXCL8; (ii) direct/indirect pro-tumorigenic effects of CXCL8 demonstrated by in vitro and in vivo studies specifically performed on thyroid cancer cells; and (iii) pharmacologic strategies proven to be effective for lowering CXCL8 secretion and/or its effects on thyroid cancer cells.

Meta-analysis of the correlation between Helicobacter pylori infection and autoimmune thyroid diseases

Objective

This study presents a systematic meta-analysis of the correlation between Helicobacter pylori (H. pylori) infection and autoimmune thyroid diseases (AITD).

Materials and Methods

Fifteen articles including 3,046 cases were selected (1,716 observational and 1,330 control cases). These data were analyzed using Stata12.0 meta-analysis software.

Results

H. pylori infection was positively correlated with the occurrence of AITD (OR = 2.25, 95% CI: 1.72–2.93). Infection with H. pylori strains positive for the cytotoxin-associated gene A (CagA) were positively correlated with AITD (OR = 1.99, 95% CI: 1.07–3.70). There was no significant difference between infections detected using enzyme-linked immunosorbent assay (ELISA) and other methods (χ2 = 2.151, p = 0.143). Patients with Grave’s disease (GD) and Hashimoto’s thyroiditis (HT) were more susceptible to H. pylori infection (GD: OR = 2.78, 95% CI: 1.68–4.61; HT: OR = 2.16, 95% CI: 1.44–3.23), while the rate of H. pylori infection did not differ between GD and HT (χ2 = 3.113, p = 0.078).

Conclusions

H. pylori infection correlated with GD and HT, and the eradication of H. pylori infection could reduce thyroid autoantibodies.

Primordial and Primary Preventions of Thyroid Disease

BACKGROUND

Primordial and primary preventions of thyroid diseases are concerned with avoiding the appearance of risk factors, delaying the progression to overt disease, and minimizing the impact of illness.

SUMMARY

Using related key words, 446 articles related to primordial and primary, preventions of thyroid diseases published between 2001-2015 were evaluated, categorized and analyzed. Prevention and elimination of iodine deficiency are major steps that have been successfully achieved and maintained in many countries of the world in last 2 decades. Recent investigations related to the effect of cigarette smoking, alcohol consumption, and autoimmunity in the prevention of thyroid disorders have been reviewed.

CONCLUSIONS

The cornerstone for successful prevention of thyroid disease entails timely implementation of its primordial and primary preventions, which must be highly prioritized in related health strategies by health authorities.

Incidence of thyroid dysfunction in an Iranian adult population: the predictor role of thyroid autoantibodies: results from a prospective population-based cohort study

Background

The prevalence of thyroid dysfunction is high in Isfahan, an area of iodine sufficient in Iran. The aim of this study is to investigate the incidence of thyroid dysfunctions in adults of metropolitan Isfahan and to determine the role of thyroid autoantibodies.

Methods

In a population-based cohort study in 2006–2011, we measured TSH, T4, T3, thyroid peroxidase antibody (TPOAb), and thyroglobulin antibody (TgAb) in 618 out of 2254 people who were euthyroid in 2006. The incidence rates per 1000 person-year (pr) were calculated. The odds ratio (OR), relative risk (RR), and 95% confidence interval (95% CI) were calculated based on logistic regression to quantify the potential predictors of thyroid dysfunction. The receiver-operator characteristic (ROC) analysis along with area under the curve (AUC) was used to determine the optimal cutoff values for baseline TPOAb and TgAb as predictors of thyroid dysfunction.

Results

Within a 6-year follow-up, the incidence rate of hypothyroidism was 3.3 in women and 2.1 in men while the incidence rate of hyperthyroidism was 3.8 in women and none in men per 1000 (person-year). A cutoff value of TPOAb at 38 IU/mL was obtained to differentiate the patients with hypothyroidism and hyperthyroidism, with specificity of 0.75 and sensitivity of 0.76, and AUC (CI 95%) of 0.882 (0.743–1.02), P = 0.01 and 0.817 (0.600–1.035) P = 0.033, respectively. There is a statistically significant association of hypothyroidism and hyperthyroidism with positive TPOAb [RR (CI 95%): 1.99 (1.27–3.13) and 2.20 (1.23–3.95), respectively].

Conclusions

The incidence rate of thyroid dysfunction is high in Isfahan, and higher TPOAb concentration is its strong predictor.

Changes in the DNA Methylation and Hydroxymethylation Status of the Intercellular Adhesion Molecule 1 Gene Promoter in Thyrocytes from Autoimmune Thyroiditis Patients

BACKGROUND

The intercellular adhesion molecule 1 (ICAM1) gene is not expressed in normal thyroid tissue but was shown to be expressed in the thyroid tissue of autoimmune thyroiditis (AIT) patients.

METHODS

This study aimed to explore whether the DNA methylation and hydroxymethylation status of the ICAM1 promoter are aberrantly altered in the thyroid cells of AIT patients and whether this change is associated with dysfunctional expression of ICAM1. A total of 35 AIT patients and 35 sex- and age-matched controls were studied. After the isolation of thyrocytes via density-gradient centrifugation, ICAM1 mRNA expression was measured using real-time PCR. The DNA methylation and hydroxymethylation status were assessed using quantitative PCR following T4 β-glucosyltransferase treatment and MspI/HpaII cleavage at -937 bp, -701 bp, -226 bp, and -65 bp upstream of the transcription start site (TSS). The DNA methylation level was verified via pyrosequencing.

RESULTS

The AIT group showed increased DNA hydroxymethylation at -937 bp and -226 bp and decreased methylation at -937 bp, -701 bp, and -226 bp upstream of the TSS. Pyrosequencing also revealed DNA hypomethylation at -708 bp, -692 bp, -690 bp, and -688 bp upstream of the TSS. The DNA methylation status at -708 bp, -692 bp, and -226 bp upstream of the TSS was negatively associated with ICAM1 mRNA expression.

CONCLUSION

In summary, we identified aberrant DNA methylation and hydroxymethylation of the ICAM1 gene promoter in the thyrocytes of AIT patients. This aberrant epigenetic modification is associated with increased expression of the ICAM1 gene.

Sex- and Age-Specific Reference Values and Cutoff Points for TPOAb: Tehran Thyroid Study

BACKGROUND

Current guidelines used for establishing reference intervals for thyroid peroxidase antibodies (TPOAb), recommended by the National Academy of Clinical Biochemistry, have been a matter of controversy. The present study sought to determine TPOAb reference intervals for different age and sex groups, as well as the TPOAb cutoff points for subclinical and overt hypothyroidism in an iodine-sufficient population.

METHODS

This cross-sectional study was conducted within the framework of the prospective Tehran Thyroid Study (TTS), in which 4174 healthy euthyroid individuals were followed for 10 years. Thyroid function tests and TPOAb were assessed.

RESULTS

The mean age ± standard deviation of participants was 39.3 ± 15.2 years. Estimated reference intervals for TPOAb corresponding to the 2.5th and 97.5th percentiles were 1.5-32.8 and 2.1-35 IU/mL in males and females, respectively. There were no significant variations in the different age groups in either sex. The optimal cutoff points for TPOAb were 18.38 and 14.77 IU/mL for predicting clinical and subclinical hypothyroidism, respectively.

CONCLUSIONS

This study establishes the reference intervals and the optimal cutoff points for TPOAb in an iodine-sufficient population.

Iodine excess as an environmental risk factor for autoimmune thyroid disease

The global effort to prevent iodine deficiency disorders through iodine supplementation, such as universal salt iodization, has achieved impressive progress during the last few decades. However, iodine excess, due to extensive environmental iodine exposure in addition to poor monitoring, is currently a more frequent occurrence than iodine deficiency. Iodine excess is a precipitating environmental factor in the development of autoimmune thyroid disease. Excessive amounts of iodide have been linked to the development of autoimmune thyroiditis in humans and animals, while intrathyroidal depletion of iodine prevents disease in animal strains susceptible to severe thyroiditis. Although the mechanisms by which iodide induces thyroiditis are still unclear, several mechanisms have been proposed: (1) excess iodine induces the production of cytokines and chemokines that can recruit immunocompetent cells to the thyroid; (2) processing excess iodine in thyroid epithelial cells may result in elevated levels of oxidative stress, leading to harmful lipid oxidation and thyroid tissue injuries; and (3) iodine incorporation in the protein chain of thyroglobulin may augment the antigenicity of this molecule. This review will summarize the current knowledge regarding excess iodide as an environmental toxicant and relate it to the development of autoimmune thyroid disease.

Enhanced iodine supplementation alters the immune process in a transgenic mouse model for autoimmune thyroiditis

BACKGROUND

The impact of excessive iodine intake on the development of autoimmune thyroiditis (AIT) is still under debate. Transgenic, antibody-devoid TAZ10 mice spontaneously develop AIT due to autoreactive thyroperoxidase-specific T cells. In this model, development of AIT is determined by a T cell infiltration of the thyroid gland leading to an elevation of serum thyrotropin (TSH) levels and significant weight gain. In the present study we investigated the impact of moderate and high iodine supplementation on the course of disease in these mice, which are immunologically prone to AIT.

METHODS

In addition to normal nutrition, mice were supplemented for 20 weeks with 2.5 μg versus 5 μg iodine per milliliter drinking water, which corresponds to a human daily iodine supplementation of 150 μg, 315 μg, and 615 μg iodine. AIT-defining parameters (weight gain, elevation of serum TSH levels, cellular infiltration of the thyroid) and immunologic effects were analyzed.

RESULTS

No significant differences were displayed when comparing weight and serum TSH levels in the iodine-supplemented versus control groups. Increased thyroid infiltrates with CD8⁺ T cells were detected by fluorescein-activated cell sorter (FACS) and immunofluorescence staining in mice supplemented with elevated iodine amounts (315 μg and 615 μg iodine per day, respectively). Immunologic monitoring revealed selective changes in immune cell frequencies (CD8⁺ and regulatory T cells, natural killer [NK] cells) and cytokine production (interferon-γ, interleukin-1α, and interleukin-17), however, without affecting the overall immune balance.

CONCLUSION

Our results demonstrate that elevated iodine supplementation has no physical impact on the course of disease in transgenic, antibody-devoid TAZ10 mice, which are immunologically prone to AIT.

Intrinsic regulation of thyroid function by thyroglobulin

BACKGROUND

The established paradigm for thyroglobulin (Tg) function is that of a high molecular weight precursor of the much smaller thyroid hormones, triiodothyronine (T3) and thyroxine (T4). However, speculation regarding the cause of the functional and morphologic heterogeneity of the follicles that make up the thyroid gland has given rise to the proposition that Tg is not only a precursor of thyroid hormones, but that it also functions as an important signal molecule in regulating thyroid hormone biosynthesis.

SUMMARY

Evidence supporting this alternative paradigm of Tg function, including the up- or downregulation by colloidal Tg of the transcription of Tg, iodide transporters, and enzymes employed in Tg iodination, and also the effects of Tg on the proliferation of thyroid and nonthyroid cells, is examined in the present review. Also discussed in detail are potential mechanisms of Tg signaling in follicular cells.

CONCLUSIONS

Finally, we propose a mechanism, based on experimental observations of Tg effects on thyroid cell behavior, that could account for the phenomenon of follicular heterogeneity as a highly regulated cycle of increasing and decreasing colloidal Tg concentration that functions to optimize thyroid hormone production through the transcriptional activation or suppression of specific genes.

High iodine blocks a Notch/miR-19 loop activated by the BRAF(V600E) oncoprotein and restores the response to TGFβ in thyroid follicular cells

BACKGROUND

Excess iodine inhibits thyroid follicular cell proliferation associated with TGFβ pathway activation, although thyroid cancers are frequently refractory to TGFβ signaling. The TGFβ pathway is predicted to be regulated by miR-17-92 cluster microRNAs. MicroRNAs are small noncoding RNAs that inhibit target mRNA translation and have emerged as potent modulators of tumorigenesis. Although the BRAF(V600E) mutation is the most prevalent alteration in thyroid cancer, the impact of iodine intake on BRAF-mediated oncogenesis remains unclear. Therefore, the aim of this study was to investigate the influence of high iodine on miR-17-92 transcriptional regulation and expression in thyroid cells expressing activated BRAF.

METHODS

Rat thyroid follicular cells that conditionally express BRAF(V600E) under doxycycline stimulation (PC-BRAF(V600E)-6) were derived from the PCCl3 line. These cells were treated with doxycycline for two days, in the absence or presence of 10 μM sodium iodide. The thyroid cancer cell lines BCPAP and KTC2 were also analyzed. Expression of the miR-17-92 cluster and Notch1 was analyzed by quantitative polymerase chain reaction, and expression of these genes was modulated by anti-miR or anti-Notch1 siRNAs transfection. Protein expression was assessed by Western blot. Luciferase assays were used to quantify Smad4 3'-UTR/miR-19 interaction and Notch signaling activation. TGFβ responsiveness was evaluated by cell cycle analysis of TGFβ-treated cells.

RESULTS

High iodine blocked BRAF(V600E)-induced upregulation of miR-17-92, including miR-19a/b. miR-17-92 promoter region analysis revealed a putative binding site for Hes1, a transcription factor responsive to Notch signaling. Notch-1 overexpression resulted in miR-19 upregulation in normal thyroid cells, while Notch-1 knockdown blocked BRAF-induced miR-19 expression. Moreover, in anaplastic thyroid cancer cells, Notch-1 knockdown reduced miR-19. Expression of BRAF(V600E) decreased Smad4 protein in normal thyroid cells. Smad4 was validated as a miR-19 target by luciferase assays, which revealed reduced luminescence associated with miR-19 interaction in Smad4 3'-UTR. Iodine treatment restored Smad4 levels in BRAF-activated cells, resulting in enhanced G1-cell cycle arrest in response to TGFβ. Moreover, this effect was mimicked in papillary thyroid cancer cells treated with anti-miR-19.

CONCLUSION

High iodine abrogates BRAF(V600E)-induced activation of miR-19, a newly identified Smad4 regulator, through Notch pathway inhibition and restores responsiveness to TGFβ signaling. Our results indicate that iodine exerts protective effects in thyroid cells, attenuating acute BRAF oncogene-mediated microRNA deregulation.

Autoimmune thyroiditis: Centennial jubilee of a social disease and its comorbidity

The history of autoimmune thyroiditis (AIT) and its role in pathophysiology of transition from adolescent hypothalamic syndrome (obesity with rose striae) into early metabolic syndrome is reviewed. Marfanoid phenotype and chronic disequilibrium between local, autacoid-mediated and systemic, hormone-mediated regulation, typical for inherited connective tissue disorders, may promote this transition. Pathogenetic roles of hyperprolactinemia and cytokine misbalance are evaluated and discussed in its pathogenesis.

CXCL8 in thyroid disease: from basic notions to potential applications in clinical practice

CXCL8 was the first chemokine shown to be secreted by thyrocytes. Experimental data suggest that CXCL8 plays a role in thyroid homeostasis but its role in thyroid diseases remains poorly investigated. Clinical studies measuring the serum levels of CXCL8 in patients with autoimmune-thyroid-diseases reported conflicting results. Solid evidences support a role of CXCL8 as a tumor-promoting agent in several human cancers. Studies in thyroid cancer are still in their initial stage, but promising. Several evidences indicate that thyroid cancer may share with other human malignancies some of the effects of CXCL8 and highlight the possibility of using CXCL8 as a marker of aggressiveness. Basic and clinical evidences in favor or against a role for CXCL8 in thyroid diseases are discussed.

Type I and type II interferons inhibit both basal and tumor necrosis factor-α-induced CXCL8 secretion in primary cultures of human thyrocytes

Interferons (IFNs) and tumor necrosis factor-α (TNF-α) cooperate in activating several inflammation-related genes, which sustain chronic inflammation in autoimmune thyroid disease (AITD). Much is known about the positive signaling of IFNs to activate gene expression in AITD, while the mechanisms by which IFNs negatively regulate genes remain less studied. While IFNs inhibit CXCL8 secretion in several human cell types, their effects on thyroid cells were not evaluated. Our aim was to study the interplay between TNF-α and type I or type II IFNs on CXCL8 secretion by human thyroid cells. CXCL8 was measured in supernatants of primary cultures of thyroid cells basally and after a 24-h incubation with TNF-α. CXCL8 was detected in thyroid cell supernatants in basal conditions (96.2±23.5 pg/mL) being significantly increased (784.7±217.3 pg/mL; P<0.0001 vs. basal) by TNF-α. Twenty-four hour incubation with IFN-γ or IFN-β or IFN-α dose dependently and significantly inhibited both basal and TNF-α-induced CXCL8 secretion. The degree of the inhibitory effect was IFN-γ>IFN-β>IFN-α. This study demonstrates that type I and type II IFNs downregulate both basal and TNF-α-induced CXCL8 secretion by human thyrocytes, IFN-γ being the most powerful inhibitor. Future studies aimed at a better comprehension of the interplay between CXCL8 and thyroid diseases appear worthwhile.

Demonstration of innate immune responses in the thyroid gland: potential to sense danger and a possible trigger for autoimmune reactions

BACKGROUND

Autoimmune thyroid disease is an archetypal organ-specific autoimmune disorder that is characterized by the production of thyroid autoantibodies and lymphocytic infiltration into the thyroid. However, the underlying mechanisms by which specific thyroid antibodies are produced are largely unknown. Recent studies have shown that innate immune responses affect both the phenotype and the severity of autoimmune reactions. Moreover, it appears that even non-immune cells, including thyroid cells, have an ability to launch such responses. The aim of this study was to conduct a more detailed analysis of innate immune responses of the thyroid upon stimulation with various "non-self" and "self" factors that might contribute to the initiation of autoimmune reactions.

METHODS

We used rat thyroid FRTL-5 cells, human thyroid cells, and mice to investigate the effects of various pathogen-associated molecular patterns (PAMPs), danger-associated molecular patterns (DAMPs), and iodide on gene expression and function that were related to innate immune responses.

RESULTS

RT-PCR analysis showed that both rat and human thyroid cells expressed mRNAs for Toll-like receptors (TLRs) that sensed PAMPs. Stimulation of thyrocytes with TLR ligands resulted in activation of the interferon-beta (IFN-β) promoter and the nuclear factor kappa-light-chain-enhancer of activated B cells (NFκB)-dependent promoter. As a result, pro-inflammatory cytokines, chemokines, and type I interferons were produced. Similar activation was observed when thyroid cells were stimulated with double-stranded DNA, one of the typical DAMPs. In addition to these PAMPs and DAMPs, treatment of thyroid cells with high concentrations of iodide increased mRNA expression of various cytokines.

CONCLUSION

We show that thyroid cells express functional sensors for exogenous and endogenous dangers, and that they are capable of launching innate immune responses without the assistance of immune cells. Such responses may relate to the development of thyroiditis, which in turn may trigger autoimmune reactions.

Interferon-γ and tumor necrosis factor-α sustain secretion of specific CXC chemokines in human thyrocytes: a first step toward a differentiation between autoimmune and tumor-related inflammation?

CONTEXT

Chemokines are chemotactic cytokines responsible for the attraction and recruitment of different cell types during leukocyte infiltration, the histopathological hallmark of autoimmunity. Previous data demonstrate that thyrocytes secrete CXC chemokines, particularly CXCL8 and CXCL10. However, the physiopathological significance of such secretion and the effects of a combination of proinflammatory stimuli in terms of preferential CXCL8 and CXCL10 release remain unclear.

OBJECTIVE

The aim of this study was to investigate whether the secretion of chemokines by human thyrocytes is a generalized inflammatory response or whether it is dependent upon specific proinflammatory stimuli.

METHODS

CXCL8 and CXCL10 were measured in supernatants of human thyrocytes in primary cultures basally and after 24 h stimulation with interferon-γ (IFNγ) (1000 U/ml) and TNFα (10 ng/ml), alone or in combination.

RESULTS

CXCL8 but not CXCL10 was detected in basal conditions. The two chemokines showed differences in their response to proinflammatory cytokines. Indeed, significant secretion of CXCL10 was induced by IFNγ (P < 0.01) and not TNFα, whereas CXCL8 was secreted in response to TNFα (P < 0.01) being inhibited by IFNγ (P < 0.01). The combination of TNFα plus IFNγ synergistically increased the IFNγ-induced CXCL10 secretion (P < 0.01) and reversed the TNFα-induced CXCL8 secretion (P < 0.01).

CONCLUSIONS

These results confirm that human thyrocytes secrete CXC chemokines and demonstrate that the secretion of CXCL8 and CXCL10 is sustained by specific proinflammatory cytokines or their combination, which ultimately determines the nature of the infiltrating lymphocytes in human thyroid diseases. These results indirectly support a major role for CXCL10 in thyroid autoimmunity whereas CXCL8 might be involved in tumor-related inflammation.

Immune manipulation for Graves' disease: re-exploring an unfulfilled promise with modern translational research

Although Graves' disease is the commonest autoimmune thyroid disorder, current therapeutics typically center on the eradication of the antigenic stimulus (i.e. thyroid gland) rather than radically tackling the underlying autoimmune processes. Consequently, it is not a surprising fact that Graves' disease remains essentially a chronic drug-dependent ailment afflicting untold numbers worldwide for decades despite progress in deciphering its autoimmune nature. Addressing the latter is key to a future cure as underscored by appropriate, albeit crude, proof-of-concept scenarios of clinical remissions achieved with hematopoietic stem cell transplantation, immune down-regulation during pregnancy, use of corticosteroids or immunosuppressives, and cytokine biologics in animal models. Ongoing basic and translational research to further elucidate and refine our understanding of the pathogenesis of Graves' disease holds the promise of unraveling novel immune manipulative techniques that will bring the world a step closer to the elusive cure of the underlying autoimmunity amidst skepticisms on the value of the science from the present lack of paralleled advances at the bedside. We review the updated literature and describe the forms of immune manipulation hitherto explored that will offer a route to a future cure, from thionamides, hematopoietic stem cell transplantation to the latest immunomodulatory agents.

Innate immune activation and thyroid autoimmunity

CONTEXT

Autoimmune thyroid disease (AITD) is the archetypal organ-specific autoimmune disorder and is characterized by the production of thyroid autoantibodies. However, the underlying mechanisms by which specific antibodies against thyroid proteins are produced are largely unknown.

EVIDENCE ACQUISITION

Published peer-reviewed basic and clinical literatures on immunology and autoimmune diseases were identified through searches of PubMed for articles published from January 1971 to May 2011. Articles resulting from these searches and relevant references cited in those articles were reviewed. All the relevant articles were written in English.

EVIDENCE SYNTHESIS

Recent studies have indicated that innate immune responses induced by both exogenous and endogenous factors affect the phenotype and severity of autoimmune reactions. One of the recent topics is the effect of self-genomic DNA fragments on immune activation. Expression of major histocompatibility complex class II on the autoimmune target cells seems to play an important role in the presentation of endogenous antigens. Accumulated evidence from animal models has generated new insights into the pathogenesis of AITD.

CONCLUSION

AITD develops by a combination of genetic susceptibility and environmental factors. Innate immune responses are associated with thyroid dysfunction, tissue destruction, and the likely development and perpetuation of AITD. In addition to the other factors, cell injury may contribute to the activation of innate immune response and the development of AITD.

Fragments of genomic DNA released by injured cells activate innate immunity and suppress endocrine function in the thyroid

Activation of innate and acquired immune responses, which can be induced by infection, inflammation, or tissue injury, may impact the development of autoimmunity. Although stimulation of cells by double-stranded DNA (dsDNA) has been shown to activate immune responses, the role of self-genomic DNA fragments released in the context of sterile cellular injury is not well understood. Using cultured thyroid cells, we show that cell injury prompts the release of genomic DNA into the cytosol, which is associated with the production of type I interferons, inflammatory cytokines, and chemokines. Molecules necessary for antigen processing and presentation to lymphocytes are also induced in thyroid cells by injury. dsDNA strongly suppressed the expression of sodium/iodide symporter and radioiodine uptake. To identify molecules responsible for sensing cytosolic dsDNA, we directly identified the cellular proteins that bound a dsDNA Sepharose column by mass spectrometry. Our analysis identified histone H2B, which was previously demonstrated to be an essential factor that mediates the activation of innate immunity induced by dsDNA. Knockdown of histone H2B using specific small interfering RNA abolished cell injury-induced innate immune activation and increased sodium/iodide symporter expression. These results indicate that genomic DNA fragments released by cell injury are recognized by extrachromosomal histone H2B, which results in the activation of genes involved in both innate and acquired immune responses in thyroid cells and suppression of thyroid function. These results suggest that sterile thyroid injury, in the absence of infection, may be sufficient to trigger autoimmune reaction and to induce thyroid dysfunction.